1. Field of the Invention
The present invention relates generally to a method for activating a fan to operate, and more particularly to a method for preventing a fan from burning down when activated to operate forward and enhancing the stability of forward operation of the fan.
2. Description of the Related Art
Along with the advance of sciences and technologies, the reliance of peoples on various electronic apparatuses has been more and more increased. In order to meet the requirements of lightweight, convenience and utility, in the current market, there is a trend to design lightweight, thin, miniaturized, multifunctional and high-processing-speed electronic products (such as computers and notebooks) as the mainstream of the electronic apparatuses. Such products can more satisfy the daily requirements in modern society.
In a power-off state, the fan impeller of a cooling fan is generally in a still state. However, when the fan impeller of the cooling fan is blown and moved backward by external return air, the fan impeller of the cooling fan will rotate backward. When the cooling fan is to be powered on to operate forward, in the case it is detected that the fan impeller rotates backward, the fan impeller will be first braked to stop backward rotating or slow down the backward rotational speed. The brake rotational speed provided by the cooling fan is increased with the increase of the return air volume. The higher the brake rotational speed is, the greater the load on the cooling fan is. When the cooling fan is powered on to operate forward, the turn-on forward voltage is likely to exceed the operational rotational speed specification due to oversized brake rotational speed. This will lead to burnout of the cooling fan or affect the stability of the operation of the cooling fan.
It is therefore tried by the applicant to provide a method for preventing a fan from burning down when activated to operate forward to solve the above problem.